It is the same flag he had for the previous two titles, stretching back to their 2005 victory over Detroit. Through Google translation:

I get asked a lot by the flag of Argentina. It is my wife (Many) who kept it has smudges of champagne.Was in the previous three festivals and is a tradition to have it, it’s like having stains other battles even looks dirty, but marks a flag that accompanies me in every achievement. And last night we returned to celebrate together something amazing.

Here’s a great shot of Ginobili with his flag, where you can see the aforementioned stains clearly. If the Ginobilis could ever bear to part with such a precious heirloom, it probably wouldn’t make a bad addition to the Basketball Hall of Fame.